Forming a hot top element by forcing slurry through penetrable mold walls



May 19, 1970 D. F. EDNELL 3,512,572

FORMING A HOT TOP ELEMENT BY FORCING' SLURRY THROUGH PENETRABLE MOLDWALLS Filed Feb. 17, 1966 3Sheets-Sheet 1 2 Q in 22 200 2 H 1 m 21 8 23200 V V 20c:

FIG.3

May 19, 1970 D. F. EDNELL 3,512,572

F'QRMlNG A HOT TOP ELEMENT BY FORCING SLURRY THROUGH PENETRABLE MOLDWALLS 5 Sheets-Sheet 2 Filed Feb. 17, 1966 FIG. 6

1979 D. .EDNELL 3512572 FORMING A HOT TOP ELEMENT BY FORCING SLURRYTHROUGH PENETRABLE MOLD WALLS Filed Feb. 17, 1966 5 Sheets-Sheet 3United States Patent FORMING A HOT TOP ELEMENT BY FORC- ING SLURRYTHROUGH PENETRABLE MOLD WALLS Daniel Fredrik Ednell, Ed, Sweden,assignor to Sandvikens Jernverks Aktiebolag, Sandviken, Sweden, acorporation of Sweden Filed Feb. 17, 1966, Ser. No. 528,256 Claimspriority, application Sweden, Feb. 19, 1965, 2,147/ 65; May 24, 1965,6,731/65 Int. Cl. B22c 1/00 US. Cl. 164--41 Claims ABSTRACT OF THEDISCLOSURE A hot top for a casting mold is prepared by filling theinterior space of a special mold form, having spaced apart wallspenetrable by liquid, with a flowable slurry of fine-grained refractorymaterial including a minor amount of an organic binder material in aliquid. Two opposed mold form walls are permeable to the liquid and suchliquid is drawn through the permeable walls either by suction orpressure in order to manufacture a hollow hot top wall.

The present invention pertains to hot tops and to a method formanufacture of hot tops or similar for casting molds, for example ingotmolds, from a composition of materials comprising in the main arefractory fine grained material and a minor quantity of a binder.Additionally the composition contains suitably a minor quantity of anorganic finely divided material of for instance fibrous structure andpossibly also a minor quantity of refractory fibrous material.

It is previously known to manufacture hot tops of this kind by mixingthe composition with a liquid and then causing it to sedimentate on apenetrable model mold, after which it is dried. The finished hot topattains a firm consistency when the binder hardens and binds theparticles of the composition together. The hot top made in this way hasa high heat insulation, low bulk weight and low heat capacity.

For obtaining the said sedimentation on the model mold it is possibleeither to subject the slurry to pressure and/or to apply a suction atthe opposite side of the model mold. The invention is based on the factthat the sedimentation may occur independently of the influence of thegravity force on the particles in the slurry and can be effected in anarbitrary direction, including laterally or upwardly. It is thuspossible to achieve a sedimentation on a model mold having two opposedpenetrable mold walls, thereby obtaining a hot top slab with a doublewall. The sides of the double wall can be interconnected by transverseconnections, which can be obtained by means of penetrable mold elementsconnecting the said opposed mold walls.

The invention appears more in detail from the following description withdrawing figures, showing:

FIG. 1, an elevational view of a model mold for making a hot top slabaccording to the invention.

FIG. 2, a cross section on the line 2-2 in FIG. 1.

FIG. 3, the same cross section as in FIG. 2 including a hot top slabmanufactured with the model mold.

FIG. 4, a cross section of an ingot mold wit-h a hot top slab of thetype illustrated in FIG. 3.

FIGS. 5-7, cross sections of an ingot mold wall with diiferentembodiments of a hot top slab according to the invention.

FIG. 8, a perspective view of a feeder according to the invention foruse with casting molds.

3,512,572 Patented May 19, 1970 FIG. 9, a cross section of the feeder inFIG. 8.

The model mold shown in FIGS. 1 and 2 is adapted for manufacture of hottop slabs. The model mold comprises two opposed parallel sides 11 and 12and intermediate sides 13, 14, 15 and 16. For forming a projection onthe hot top slab a recess is formed in the side 11, limited by the side14 and two small sides 17 and 18. All of the said sides are made of apenetrable material, for instance a net, as indicated in FIG. 1 byreference 19. Said net is supported at its outside by a frameconstruction 20, for instance a grid 20a: or a net having greateropenings than the net forming the side surfaces. The mold is divided bya joint 21, in order that the two parts can be separated from eachother.

For producing supporting connections between the side 'walls of the slabwhich is cast in the mold there are conical mold elements attached tothe mold wall 11 and extending toward the wall 12, said elements alsobeing penetrable.

For supplying the slurry which is intended to sedimentate on the moldwalls there are a number of short tubes 23 through the Wall of the modelmold. The slurry is supplied through the tubes 23 to the inside of themold and is subjected to pressure from the inside and/or suction fromthe outside. This results in that the suspending liquid is squeezed outthrough the mold walls, the material suspended in the liquidsedimentating on the walls. In this way a slab 30 is formed which isillustrated in FIG. 3. The slab has a double wall section comprising twosides 31 and 32 separated by an intermediate space 33. The model mold issuitably made with penetrable edge sides 13-16 around the edges of thesides 11 and 12, so that the cavity 33 is closed except at the holes inthe slab left by the tubes 23. Said tubes can possibly have an oblongsection in the longitudinal direction of the mold in order to obtain amore even distribution of the composition. At the mold wall 13 is thusformed an edge side 34 and at the mold Wall 14 an edge side 35 and aprojection 36 at the mold sides 17 and 18. At the conical mold elements22 there are formed conical connections 37 between the sides 31 and 32,which give the slab a higher internal strength against the pressure ofcast metal when the slab is used.

In FIG. 4 is illustrated how the hot top slab 30, shown in FIG. 3, ishung on the wall of an ingot mold 40. It is assumed in this case thatthe hot top consists of a number of separate slabs which are hung up atthe inside of the ingot mold around the upper part thereof.

In FIG. 5 is shown another embodiment of a hot top 41 hung on an ingotmold 40 by means of suspension means not illustrated as for examplebooks of steel wire. The hot top has in this case a triangular crosssection with a vertical wall 42 and an inclined wall 43 which at theirlower edges are joined to wedge shape and at their upper ends are joinedby a horizontal wall 44. The slab 41 is shown without the conicaltransverse connections 37, which are illustrated in the slab 30 in FIG.3, but of course it is possible to have such connections also in theslab 41 if necessary. In the cavity 33 in the slab 30 as well as in thecavity 45 in the slab 41 can be filled an insulating, possiblyexothermic material, through the holes 38 and 46 respectively.

FIG. 6 shows a hot top slab 50 applied to an ingot mold 40. The two wallportions 51 and 52 are integrally interconnected only at their loweredges by a wall portion 53. The space 54 between the wall portions isopen at the upper end and a separate support body is inserted into thespace, consisting of a frame 55 holding a number of support pieces 56abutting against the inside of the wall portions 51 and 52. The supportbody has the same function as the conical portions 37 in FIG. 3, i.e.

3 to prevent the side 51 of the slab facingthe cast metal from beingbroken.

FIG. 7 shows a hot slab 60 with a V-shaped cross section. The slabcomprises an outer side 61 and an inner side 62, which are joined attheir lower edges and diverge upwardly with a space 63 between them. Thespace 63 is open at the upper end, which can be obtained by pro viding asolid wall and omitting the penetrable mold wall at this part. A supportbody 64 can be inserted into the space 63, said body being solid orhaving a powder consistency and possibly consisting of an exothermicmaterial.

The use of the invention has been described above for hot topscomprising a number of separate slabs, but it can also be used formaking hot tops in one piece for instnce as a hood which is placed ontop of an ingot mold with a supporting collar around it. A use of theinvention similar to the last mentioned is for feeders in casting moldsin foundries, and FIGS. 8 and 9 show a feeder 70 made according to theinvention. It is cylindrical with an annular cross section, the wallcomprising an outer wall 71 and an inner Wall 72, between which thereare spaces 73. In the illustrated embodiment the spaces 73 are separatedby intermediate walls 74, but the latter can possibly be omitted,leaving an uninterrupted annular space. In this case the walls 71 and 72are held together by the transverse connections at the lower and upperends of the feeder. The upper end has holes 75 which are formed by thetubes for supply of slurry when manufacturing the feeder.

As appears from the above the mold element formed according to theinvention consists of a body with a double wall comprising two opposedwall portions. These wall portions are interconnected integrally and inone piece by one or more connections situated between them. The twoopposed wall portions can be in the main equally thick, but it may oftenbe advantageous to make the wall portion situated adjacent the castmetal somewhat thicker in order to increase the ability of the wall toresist the pressure from the cast metal. This can be achieved forinstance by turning the side of the model mold downwardly at which thethicker wall portion is wanted, as illustrated in FIGS. 2 and 3. In thisway the gravity force causes a more rapid sedimentation at the lowerside of the mold, the layer sedimentating thereon becoming thicker. Itis also possible to use mold sides with diiferent degrees ofpenetrability in order to regulate the thicknesses of the sedimentatedlayers. The thickness of the layer adjacent the cast metal can bel.252.0, preferably 1.4-1.6 times the thickness of the opposite wallportion. The wall portion adjacent the cast metal can' suitably have athickness of 10-30 mm. in the type of hot top illustrated in FIG. 4. Inother embodiments of hot tops the thickness may be greater than the saidupper limit.

The hot top according to the invention consists essentially of finelydivided particles and a binder connecting of binder. For the actualpurpose a resin glue is suitable,

said particles. At least a major part of the particles con- 7 sists of afine grained refractory material, for instance olivine or quartz.Additionally the composition of in the hot top can suitably contain aminor quantity of organic particles, for instance of a fibrous structureas finely divided paper pulp or wood pulp, or of a cellular structure ascork. The composition can also advantageously contain particles of afibrous refractory material as asbestos, glass wool or rock wall. Theparticles in the composition should have such a size that they can bemixed with a suspending liquid to a slurry and then be caused tosedimentate on a model mold according to the above. The binder should besoluble or mixable in the suspending liquid and should be added to sucha concentration that the finished hot top contains the desired quantityand said glue may be synthetic.

After being formed in the model mold by sedimentation of particles ofthe composition the formed object is removed and dried at a temperatureof -200 C., usually l60 C. There is thus no sintering, but thecomposition is held together by the dried and/or hardened binder. Thefibrous material contributes to the cohesion.

As an example of a composition which is suitable for the present purposecan be mentioned a mixture containing 82-94% by weight fine grainedrefractory mateterial, 39% by weight finely divided organic material offibrous or cellular structure, 18% by weight binder and possibly a minorquantity, preferably up to 5% by weight of a fibrous refractorymaterial.

The invention provides the advantage that the double wall gives theinsulating hot top element a very high heat insulation. Also the heatcapacity is low. It is possible to add an exothermic material to the hottop element without letting thismaterial come in contact with the castmeal. A further substantial advantage is that all the sides of he hottop element can be exactly shaped with regard to the future use.

I claim:

1. Method for the manufacture of a hot top element which comprisesdelivering a slurry of a composition consisting essentially of a majorportion of a fine grained refractory material and a minor portion of abinder in a liquid to the interior of a mold having spaced apart wallspart of which are situated closer to each other than other parts, whichwalls are penetrable by said liquid, causing sedimentation of solids ofsaid slurry over the interior surfaces of the mold by creating andmaintaining such a higher pressure of slurry within the mold than theambient atmospheric pressure that sedimentation can occur laterally andupwardly as well as downwardly thereby depositing a hollow structurewith spaced apart walls, which partially are integrally interconnected,and drying said structure.

2. Method as defined in claim 1 in which one wall of said mold ispositioned substantially horizontally and below another wall whereby thethickness of said composition on said one wall is made greater than thethickness on said other wall.

3. Method as defined in claim 1 in which said mold walls aresubstantially parallel and are connected at an edge of each wall by apenetratable transverse wall.

4. Method as defined in claim 1 in which said mold walls are at an acuteangle to each other and are connected to each other at one edge of eachWall.

5. Method as defined in claim 1 in which spaced apart, conical,penetratable projections extend from one of said mold walls toward theother of said mold walls.

References Cited UNITED STATES PATENTS 3,123,878 3/1964 Davidson 164-138X 3,250,839 5/1966 De Luca 264-86 X 3,321,171 5/1967 Gorka et al.164-138 X 1,336,180 4/1920 Allen et al.

3,460,606 8/1969 Boddey 164-43 X FOREIGN PATENTS 1,370,665 7/ 1964France.

ROBERT D. BALDWIN, Primary Examiner US. Cl. X.R.

